Boiling water, baking soda and vinegar method
For tough blockages, pour boiling water down the drain. This is only recommended for kitchen sinks or bathroom vanity sinks. Mix the boiling water with ½ cup of baking soda and pour.
Wait 5 - 10 minutes.
Next, pour a cup of vinegar down the drain and wait another 10 - 15 minutes. This should clear up most clogs at this point. Just remember to follow up these steps with warm water.
Credit to Adeola Fayehun